Cook fresh noodles or dry spaghetti in a
large pot of boiling water, until they are just underdone. Drain and set
aside.

Heat a wok or large frying pan over high heat. Add the
oil, then the beef, and cook, stirring and breaking up the beef as you
go, until the beef is lightly browned. Add scallions and mushrooms, and
continue stir-frying until the mushrooms are starting to brown. Stir in
the chili paste, oyster sauce and soy sauce, then add the noodles and
stir to combine everything. Top with bean sprouts, and serve hot.